This invention relates to methods for industrial cleaning and, more particularly, to chemical methods and solutions for removing surface contaminants from industrial apparatus and transportation devices, such as automobiles, trucks, and the like.
Washing systems are generally of two types: abrasive (brushes) and chemical (without brushes). The more common system utilizes brushes or other scrubbing devices which operate against the surface of a device to remove surface contaminants. While the brush-type is effective in removing surface dirt, the mechanical agitation of brushes may produce deliterious abrasion of a painted surface. In addition, such brush-type systems can damage accessory equipment such as mirrors, antennas, decorative trim, or other appurtenances.
In a brushless operation, chemical action and agitation from high pressure streams or jets of various solutions are directed against the surface to be cleaned. Early systems used alkaline detergent solutions as the sole cleaning solution. However, such high pressure solutions were not entirely effective to remove the adherent film of contaminants present on most devices, particularly vehicles. On transportation devices this contamination is particularly evident as an adherent film on ferrous or non-ferrous surfaces as bumpers and wheel rims. Such adherent road film may contain materials originating from soils, exhaust emissions, tire wear, cement, rust and road salt.
A second procedure was devised to remove the adherent road film, still without agitation. Particular procedures were developed to use a combination of acid and alkali detergent solutions in sequence. However, the corrosive attack of the effective solutions on glass, aluminum, magnesium and ferrous components has precluded any widespread adoption and use of the basic procedure.
Yet a further approach to a brushless washing procedure includes acidic formulations containing a detergent builder, preferrably selected from the alkali metal phospates or bisulfates, and a fluoride compound. The device to be cleaned was first wholly wetted with a jet of used or reclaimed acid solution having a pH in the range of 4.5-5.0 at a pressure effective to mechanically remove major surface contamination; then contacted with a jet of first fresh acid solution having a pH of 4.5-5.0 and generally without a fluoride compound; and finally, contacted with a heated mist of a second fresh acid solution including fluoride compounds. After the acid applications, the device was then rinsed with a jet of alkaline solution followed by a jet of water. Application of the solutions was from fixed nozzles and the acid solutions were formed with low concentrations of active ingredients to minimize costs.
The above procedure generally removed light adherent film contamination without noticeable damage to aluminum, magnesium or other ferrous components, but strongly bound contamination, forming a tenaciously adherent road film comprised mainly of hydrocarbon-soil matrix, are not removed. If the concentration of active ingredients is increased to accomodate heavy contamination, substantial protective film removal from the surface is obtained even in a single cycle, and, although cleaning is improved, there still remains surface contamination. Also, the cost of the cleaning cycle substantially increases due to increased chemical usage.
In yet another attempt, a low concentration acid solution (about 1.5 weight percent active ingredients) is applied over an entire dry vehicle and rinsed with an alkaline solution. The cleaning capability of this process may be slightly improved over the above procedures, but the sensitivity of protective film removal to the applied ingredient concentrations was increased.
The disadvantages of the prior art are overcome by the present invention, however, and improved methods are provided for industrial cleaning in a brushless, or chemical, system.